10.3.1 MockGriffonApplication

`MockGriffonApplication` is a fully functional GriffonApplication with the advantage that it lets you override the location of all configuration classes: `Application`, `Builder`, `Config` and `Events`.

> If you choose to change the default `UIThreadHandler` then you must do it so right after the application has been instantiated and no other operation that requires multi-thread access has been called, otherwise you won't be able to change it's value.

By default, a MockGriffonApplication defines the following:

- `MockApplication` - setups a 'mock' MVC group with 3 elements: `MockModel`, `MockView` and `MockController`
- `MockBuilderConfig` - defines a single builder entry: `griffon.test.mock.MockBuilder`
- `MockConfig` - defines a single config entry: `mocked = true`
- `MockEvents` - defines an event handler for 'Mock'

The remaining classes have these settings:

- `MockBuilder` - a single node named `mock` that returns a map with any properties that were defined on the node.
- `MockModel` - a lone observable property `value` of type String.
- `MockView` - simple script that calls the `mock` node defined by the builder.
- `MockController` - a controller with no actions.